[Bugfix] Fix DeepSeekV31ToolParser to correctly parse multiple tools in non-streaming output (#25405)

Signed-off-by: taohui <taohui3@gmail.com>

tests/tool_use/test_deepseekv31_tool_parser.py

@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import pytest
+
+from vllm.entrypoints.openai.tool_parsers import DeepSeekV31ToolParser
+from vllm.transformers_utils.tokenizer import get_tokenizer
+
+MODEL = "deepseek-ai/DeepSeek-V3.1"
+
+
+@pytest.fixture(scope="module")
+def deepseekv31_tokenizer():
+    return get_tokenizer(tokenizer_name=MODEL)
+
+
+@pytest.fixture
+def parser(deepseekv31_tokenizer):
+    return DeepSeekV31ToolParser(deepseekv31_tokenizer)
+
+
+def test_extract_tool_calls_with_tool(parser):
+    model_output = (
+        "normal text" + "<｜tool▁calls▁begin｜>" +
+        "<｜tool▁call▁begin｜>foo<｜tool▁sep｜>{\"x\":1}<｜tool▁call▁end｜>" +
+        "<｜tool▁calls▁end｜>")
+    result = parser.extract_tool_calls(model_output, None)
+    assert result.tools_called
+    assert len(result.tool_calls) == 1
+    assert result.tool_calls[0].function.name == "foo"
+    assert result.tool_calls[0].function.arguments == "{\"x\":1}"
+    assert result.content == "normal text"
+
+
+def test_extract_tool_calls_with_multiple_tools(parser):
+    model_output = (
+        "some prefix text" + "<｜tool▁calls▁begin｜>" +
+        "<｜tool▁call▁begin｜>foo<｜tool▁sep｜>{\"x\":1}<｜tool▁call▁end｜>" +
+        "<｜tool▁call▁begin｜>bar<｜tool▁sep｜>{\"y\":2}<｜tool▁call▁end｜>" +
+        "<｜tool▁calls▁end｜>" + " some suffix text")
+
+    result = parser.extract_tool_calls(model_output, None)
+
+    assert result.tools_called
+    assert len(result.tool_calls) == 2
+
+    assert result.tool_calls[0].function.name == "foo"
+    assert result.tool_calls[0].function.arguments == "{\"x\":1}"
+
+    assert result.tool_calls[1].function.name == "bar"
+    assert result.tool_calls[1].function.arguments == "{\"y\":2}"
+
+    # prefix is content
+    assert result.content == "some prefix text"